For CI - cache the MinGW tool directories without invalidator.

The .travis.yml file turns out to be a bad invalidator as well because it is also mutating between normal and MinGW CI builds.

.appveyor.yml

@@ -31,8 +31,8 @@ cache:
   # Build
   # mingw-Build
   # Cache the MinGW compiler toolchains so that our CI builds do not chalk up their download stats
-  - C:\tools\mingw32 -> .travis.yml
-  - C:\tools\mingw64 -> .travis.yml
+  - C:\tools\mingw32
+  - C:\tools\mingw64
 environment:
   GIT_NAME:
     secure: onlJNy/nGFT1GXNdusL4jokojSPZ732EFaXwdhPnpM0=

.travis.yml

@@ -138,8 +138,8 @@ cache:
   # Build
   # mingw-Build
   # Cache the MinGW compiler toolchains so that our CI builds do not chalk up their download stats
-  - C:\tools\mingw32 -> .travis.yml
-  - C:\tools\mingw64 -> .travis.yml
+  - C:\tools\mingw32
+  - C:\tools\mingw64
 environment:
   GIT_NAME:
     secure: onlJNy/nGFT1GXNdusL4jokojSPZ732EFaXwdhPnpM0=